A special MR sign of brainstem infarction

Objective To define the hemi-section sign,and investigate its MR characteristics,pathogenesis and relation with vascular territories.Methods Clinical and conventional MRI data were collected from 286 patients with brainstem lesions from January to April 2009.MR findings,pathogenesis and anatomic basis of the hemi-section were analyzed.Results The hemi-section was found in 35 of 286 patients,and all lesions of these 35 cases were confirmed as brainstem infarction,showing a unilateral anteromedial brainstem infarct sharply marginated at the midline.All lesions in the 35 cases were located in unilateral anteromedial zones,1(2.9%) located at the midbrain,32(91.4%) located at the pons and 2(5.7%) located at the medulla oblongata.Conclusion The hemi-section sign,consistent with branches and distribution of the brain stem artery,is special in brainstem infarction and mostly occurs in the pons.This sign plays an important role in the diagnosis of brainstem infarction and in the differential diagnosis of brainstem lesions.